Mystery of the “Fungus-Eating Plant” Solved

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Reviewed by Lily Ramsey, LLMJan 27 2025

A researcher from Kobe University has uncovered the function of a structure that inspired the name of a fungus-eating orchid over 130 years ago. This discovery sheds light on a previously unknown method plants use to ensure reproduction.

Between 1887 and 1957, renowned Japanese botanist Tomitaro Makino named approximately 1,000 plant species and identified around 600 new ones. Among his notable findings was the 1889 discovery of the small orchid Stigmatodactylus sikokianus. The plant was named for its distinctive finger-like projection on the stigma—the female part of the flower that collects pollen—referred to as the “dactylus.” Despite the plant’s status as a well-known Japanese orchid, the function of this structure had remained a mystery.

Kenji Suetsugu, a botanist at Kobe University who specializes in orchids that rely on soil fungi for sustenance rather than sunlight, decided to investigate. “I am particularly interested in their pollination mechanisms, employing an interdisciplinary approach that integrates taxonomy, ecology, and evolutionary biology,” Suetsugu explained. His curiosity led him to question the purpose of the finger-like appendage and its ecological role.

To address these questions, Suetsugu meticulously observed whether insects visited the flowers, the conditions under which the plants produced seeds, and the morphology of the flowers throughout their growth stages. His findings, published in the journal Plants, People, Planet, revealed that the orchid primarily self-pollinates, without depending on insects to transfer pollen between plants. This self-pollination occurs roughly three days after the flowers open, a delay with important ecological implications.

The plants, which grow in the dark forest understory, often among leaf litter, do not produce nectar to attract pollinators. As a result, insect visits are infrequent. “While self-pollination likely ensures reproductive success, it also carries the risk of inbreeding,” Suetsugu noted. “This may drive the evolution of mechanisms that combine the advantages of self-pollination with opportunities for outcrossing. Delayed self-pollination, occurring only after potential outcrossing has failed, is likely one such adaptive strategy—a failsafe mechanism.”

Microscopic analysis revealed the role of the finger-like appendage in this process. Three days after the flower opens, the stigma collapses and, together with the appendage, comes into contact with the pollen-carrying anther. This positioning allows pollen tubes to grow through the appendage into the stigma and eventually into the ovary, completing fertilization.

“The movement of the stigma appendage represents, as far as we know, a unique self-pollination mechanism in orchids,” Suetsugu stated. “The most exciting part of this study was uncovering this previously unknown mechanism, which highlights the remarkable evolutionary strategies plants can develop to ensure survival.”

With 28 species in the Stigmatodactylus genus, many of which have similar structures, this mechanism could be widespread among related orchids.

Suetsugu emphasized the study's broader implications, noting, “This discovery bridges historical botanical research and modern scientific inquiry. It demonstrates the value of integrating taxonomic, ecological, and evolutionary approaches to uncover new insights. In an age of increasing research specialization, this study shows that traditional natural history research still has immense potential to reveal novel phenomena.”